Carbon is an unincorporated rural hamlet in Douglas Township, Adams County, Iowa, United States. The population was 36 at the 2020 census. There is a church at Carbon, and a community center, and no other businesses or services.

Adams County is a county in the U.S. state of Iowa. As of the 2020 census, the population was 3,704, making it Iowa's least-populous county. Its county seat is Corning.